As detectors of alpha rays among those of radiant rays, detectors that include ZnS scintillators have been known, for example. The ZnS scintillators emit light when the alpha rays enter. On the other hand, there are alpha ray observation devices that use the fact that alpha rays cause nitrogen in the atmosphere to emit light, and detect alpha rays by observing light emitted from the nitrogen to allow alpha rays to be observed even from a remote site. The emitted light is ultraviolet rays.
FIG. 9 is a configuration diagram showing a conventional example of an alpha ray observation device that detects alpha rays through observation of light emitted from nitrogen.
The alpha ray observation device as shown in FIG. 9 has been known; the device includes a condenser lens 101 that condenses light emitted from nitrogen, a wavelength selecting element 102 that extracts light emitted from nitrogen from the condensed light, an optical element 103 that divides the extracted light emitted from nitrogen into transmitted light and reflected light, a direction changer 104 that changes the propagation direction of the reflected light, optical detectors 105a and 105b that receive the transmitted light and the reflected light and count the number of photons, and a signal processor 106 that selects the light emitted from nitrogen due to alpha rays by causing the optical detectors 105a and 105b to measure the transmitted light and the reflected light simultaneously.